You can read the last FAQ answer in the page source:

We love open source and community projects, so we have decided to make TalkJS entirely free for non-commercial purposes.

When you go live, there's a button you can click to let us know you're using TalkJS non-commercially, and you'll be able to go live without paying.

Note: The non-commercial TalkJS license includes no support. If need want the certainty of access to our great customer support, please become a paying customer.